This invention pertains to an improved well completion for electrical power transmission to a subsurface formation. More particularly, power transmission efficiency is increased using a lower part of the casing as the electrode and insulated nonmagnetic metal upper casing as the primary conductor.
Large deposits of viscous hydrocarbonaceous substances are known to exist in subterranean formations such as for example, the Ugnu formation in Alaska. Many techniques have been proposed for producing tar sands and viscous oils. Relatively recently it has been proposed, for example, in U.S. Pat. Nos. 3,642,066; 3,874,450; 3,848,671; 3,948,319; 3,958,636; 4,010,799 and 4,084,637, to use electrical current to add heat to a subsurface pay zone containing tar sands or viscous oil to render the viscous hydrocarbon more flowable. Two electrodes are connected to an electrical power source and are positioned at spaced apart points in contact with the earth. Currents up to 1200 amperes are passed between the electrodes. The effectiveness of the process, therefore, depends on power transmission efficiencies. It is the primary purpose of this invention to provide an electrical power transmission well completion system of reduced impedence and power losses.